1. Field of the Invention
The present invention relates generally to automotive pulleys and a method of making and, more specifically, to a pulley made from composite material which is capable of withstanding the extreme forces exerted of an automotive engine environment.
2. Description of Background Art
The automotive industry is currently working diligently toward meeting increased fuel economy and pollution control standards. Central to these objectives, weight reduction has become a major focus among the automotive manufacturers and their numerous suppliers. A reduction in vehicle weight results in improved fuel economy which corresponds with reduced pollution output.
For many years, the automotive industry has attempted to replace heavier metal components with components made from lighter composite materials. One area of focus in this effort has been the replacement of the metal pulleys used in the belt drive system of an internal combustion engine. Virtually all automotive vehicles use a drive belt and a series of pulleys in order to drive the various vehicle accessories, such as the alternator, air conditioning unit, power steering system, engine fan, and air pump. The drive belt which drives each of these accessories is driven by a pulley that is commonly connected to the crank shaft of the internal combustion engine.
An exemplary belt drive system is shown in FIG. 10, in which a belt 10 is driven by a pulley 12 connected to a crank shaft of the internal combustion engine (not shown). The belt 10 is in driving engagement with a pulley 14 which is connected to a fan. The belt 10 also drives a series of pulleys associated with an air pump 16, an alternator 18, an air conditioning unit 20, and a power steering unit 22. An idler 24 is provided for maintaining the tension in the belt 10. In FIG. 9, a serpentine drive belt 10 is shown in driving connection with an alternator pulley 18 which is mounted to an alternator drive shaft 28 of alternator 30.
Of all the pulleys in the belt drive system, the alternator pulley is exposed to the highest forces. Heretofore, the automotive industry has not developed a pulley made of light weight composite material which is capable of withstanding the forces imposed upon an alternator pulley. In particular, the prior pulley designs have suffered from the drawback that the materials tested lack the requisite surface hardness or are unstable under the extreme forces and high temperatures to which they are exposed in a belt drive system of an internal combustion engine. In particular, an internal combustion engine typically runs at approximately 20,000 rpm while the pulley associated with the alternator is commonly driven at approximately a 3 to 1 ratio with respect to the engine rotation which yields an alternator pulley rotation of approximately 60,000 rpm. In addition, the temperatures under the hood of an automotive vehicle are commonly above 200.degree. F. and the vibrations that the pulleys are exposed to are extremely intense.
The automotive industry has also strived to reduce noise and vibration. Composite materials have been known to contribute to noise and vibration reduction in many applications. The reduction of noise and vibration associated with composite materials is generally attributable to the dampening effect of the molecular structure of the composite materials.
Occidental Chemical Corp. and its Durez Division have produced a line of pulleys made from a composite material called phenolics. Phenolics is a thermoset material which generally means that the material is a high molecular weight polymer that solidifies or "sets" irreversibly when heated. Thermoset materials also often require the addition of "curing" agents. Phenolics pulleys have proven to be acceptable for certain applications in the automotive industry. For example, the phenolics pulleys have been incorporated into the power steering assemblies of a line of cars and light trucks. However, the pulleys which are used on the power steering assemblies are not exposed to the high forces that are applied to an alternator pulley and phenolics pulleys have been found to be too brittle and unstable to withstand the forces required for alternator pulleys.
It is therefore desirable to provide a light-weight automotive pulley which is capable of withstanding the forces exerted thereon when assembled on an alternator of an internal combustion engine.